Genus Sialis - Nearctic Alderflies

Sigh-AL-is

Sialis Latreille 1802

From Greek sialis (σιαλις, also sialemdris-- σιαλεμδρις), a type of bird (1) (2). This was derived from the Greek word siali, meaning spittle or grease (1), and referred to a sibilant (hissing) noise made by the bird (Gruson, 1972, Words for Birds, pp. 209-210; Gruson gives the original Greek source as a work by Athenaeus). Though The Century Dictionary states that the name Sialis (insect) refers to the bird sialis, it seems more likely that Latreille had the original "greasy" meaning in mind, since the wings of Sialis are shiny, or greasy, in appearance.

This is the only Nearctic genus. There are 24 Nearctic species in the genus.

Most are 9-10 mm (3), up to 18 mm length to folded wingtips (4) (5).

Black or dark brown insects that hold their heavily-veined wings folded roof-like over their backs. Lack ocelli. Antennae roughly half the body length. Fourth tarsal segment widened, has two lobes. Reminiscent of the Dobsonflies and Fishflies, but the Alerflies are considerably smaller. Wing venation:

  

Identification of species requires examination of microscopic characters--genitalia of males. Sialis infumata, Sialis americana, and Sialis mohri are widespread species. Sialis infumata represents a species group (5).

Much of North America

Adult typically found on vegetation near streams, ponds--the larval habitat. Quoting from A Guide To The Megaloptera And Aquatic Neuroptera Of Florida (5):

Larvae of Sialis prefer soft substrates (mud, silt, detritus) with plant debris accumulations...; there the larvae burrow and feed on detritus, as well as invertebrate prey such as chironomids, tubificid worms, and ostracods .... Many species are associated with specific waterbody types, for instance S. joppa is found primarily in small streams, whereas S. itasca is associated with lakes; other species such as S. americana and S. vagans are known from both lakes and streams.

Typically May-June in much of range. April-July (various species, North Carolina). April-May (Kansas). As early as March in Texas (6).

Adults feed little, if at all. Larvae are predatory on aquatic invertebrates.

Larvae are aquatic:

  

Pupation takes place above water level. Mating takes place at night. Eggs are laid near water and larvae crawl to it. Pupae overwinter.

Borror, entries for sialis, siali (1)

The Century Dictionary, entry for Sialis (genus) (2)

Milne, pp. 520-521, fig. 331--adult (3)

Arnett, p. 344 (4) describes S. infumata, a widespread eastern species.

A Guide To The Megaloptera And Aquatic Neuroptera Of Florida, pp. 23-28 (5)

Taber, p. 205, describes identification issues, mentions flight period in Texas (6).

Swan and Papp, p. 182, fig. 190--illustration of larva, adult of S. fumans, describes other species (7)

Brimley, p. 29 (8), lists three species for North Carolina, gives flight dates of April-June.

Salsbury, p. 153--photo of adult S. infumata (9)

White, Field Guide to Insects (10)